Stream levels, stream flow discharge, and reservoir and lake levels are monitored by the United States Geological Survey (USGS) at thousands of locations across the U.S. Real-time hydrologic conditions are available at over 8,000 sites and daily data are available at over 24,000 sites.

A tutorial for using this site, written by the USGS, can be accessed here. A second tutorial can be accessed here. Immediately following this page in the MWS Module are 2 interactive lessons that walk you through accessing and downloading USGS stream flow data from the NWIS site and bringing it into Excel to graph. You will access these lessons simply by moving to the next page in the module by using the right-arrow button (upper-right of your screen).

One of the measurements provided on the USGS Real-Time stream site is gage height. Gage height is a measurement of the height of the water in the stream at the point of the measurement.

A second measurement provided by the USGS website is discharge (Q), in cubic feet per second (cfs). The relationship between stream flow discharge and gage height is typically not linear. This is because stream banks are rarely vertical, but instead are sloping. As a result, the volume of water passing through a stream at a gage height of 3 feet may be double the volume of water passing through a stream at a gage height of 2 feet.

If desired, data can be downloaded from the USGS site as a tab-delimited text file for further analysis on your own computer.

County Level Stream Monitoring

Stream level data are also monitored across Arizona at the county level. These data can be accessed here. Data can also be downloaded from this site in comma-delimited text format.